The proposed research concerns the molecular pathology of human hemoglobin variants and of other hemoglobinopathies, which are recognized in so many millions of individuals with hematological disorders. Emphasis will be placed on studies concerning the relation between functional (and clinical) symptoms and abnormal properties due to alterations in structure. In addition, the importance of some new genetic developments, notably those concerning the multiplicity of hemoglobin structural genes and the existence of silent structural genes, will be further evaluated, so that perhaps a better insight in the genetic basis of inherited hematological disorders, the various forms of thalassemia in particular, will be obtained. Comparative studies on the structure, biology and genetics of hemoglobins in selected animal species may implement our understanding of the control of genetic expression in both normal and pathological conditions.